Method and device for transmitting or receiving wireless signal in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system and, more particularly, to a method and a device therefor, the method comprising the steps of: receiving scheduling information relating to uplink data; and transmitting the uplink data through a time slot having a plurality of symbols by using the scheduling information, wherein: when a reference signal for beam-arrangement is not transmitted in the time slot, a transmission beam direction of the uplink data remains the same in the time slot; and when the reference signal for beam-arrangement is transmitted in the time slot, the transmission beam direction of the uplink data is changed according to a transmission beam direction of the reference signal for beam-arrangement, in a symbol at which the reference signal for the beam-arrangement is transmitted in the time slot.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/476,516, filed on Jul. 8, 2019, which is the National Stage filingunder 35 U.S.C. 371 of International Application No. PCT/KR2018/000337,filed on Jan. 8, 2018, which claims the benefit of U.S. ProvisionalApplication No. 62/443,620, filed on Jan. 6, 2017, the contents of whichare hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and device for transmitting/receiving awireless signal. The wireless communication system includes a CA-based(Carrier Aggregation-based) wireless communication system.

BACKGROUND ART

Generally, a wireless communication system is developing to diverselycover a wide range to provide such a communication service as an audiocommunication service, a data communication service and the like. Thewireless communication is a sort of a multiple access system capable ofsupporting communications with multiple users by sharing availablesystem resources (e.g., bandwidth, transmit power, etc.). For example,the multiple access system may include one of CDMA (code divisionmultiple access) system, FDMA (frequency division multiple access)system, TDMA (time division multiple access) system, OFDMA (orthogonalfrequency division multiple access) system, SC-FDMA (single carrierfrequency division multiple access) system and the like.

DISCLOSURE Technical Problem

An aspect of the present disclosure devised to solve the conventionalproblem is to provide a method of efficiently transmitting/receiving awireless signal in a wireless communication and an apparatus therefor.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present disclosure, a method of transmitting anuplink signal by a user equipment (UE) in a wireless communicationsystem includes receiving scheduling information for uplink data, andtransmitting the uplink data in a time slot including a plurality ofsymbols based on the scheduling information. If a reference signal (RS)for beam alignment is not transmitted in the time slot, a transmissionbeam direction of the uplink data is maintained the same in the timeslot, and if the RS for beam alignment is transmitted in the time slot,the transmission beam direction of the uplink data is changed to match atransmission beam direction of the RS for beam alignment in a symbolcarrying the RS for beam alignment in the time slot.

In another aspect of the present disclosure, a UE used in a wirelesscommunication system includes a radio frequency (RF) module and aprocessor. The processor is configured to receive scheduling informationfor uplink data, and to transmit the uplink data in a time slotincluding a plurality of symbols based on the scheduling information. Ifan RS for beam alignment is not transmitted in the time slot, atransmission beam direction of the uplink data is maintained the same inthe time slot, and if the RS for beam alignment is transmitted in thetime slot, the transmission beam direction of the uplink data is changedto match a transmission beam direction of the RS for beam alignment in asymbol carrying the RS for beam alignment in the time slot.

An original transmission beam direction configured for the uplink datamay be different from the transmission beam direction of the RS for beamalignment.

If the transmission beam direction of the uplink data is changed tomatch the transmission beam direction of the RS for beam alignment, anRS for demodulation of the uplink data may additionally be transmittedin one or more symbols carrying the RS for beam alignment.

The transmission beam direction of the RS for beam alignment may bechanged on a symbol group basis in the time slot, and the transmissionbeam direction of the uplink data may also be changed on a symbol groupbasis to match the transmission beam direction of the RS for beamalignment.

The wireless communication system may include a 3^(rd) generationpartnership project (3GPP)-based wireless communication system.

Advantageous Effects

According to the present disclosure wireless signal transmission andreception can be efficiently performed in a wireless communicationsystem.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure, illustrate embodiments of thedisclosure and together with the description serve to explain theprinciple of the disclosure. The technical features of the presentdisclosure are not limited to specific drawings and the features shownin the drawings are combined to construct a new embodiment. Referencenumerals of the drawings mean structural elements.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

FIG. 2 illustrates a radio frame structure.

FIG. 3 illustrates a resource grid of a downlink slot.

FIG. 4 illustrates a downlink subframe structure.

FIG. 5 illustrates an example of an Enhanced Physical Downlink ControlChannel (EPDCCH).

FIG. 6 illustrates configuration of cell specific reference signals(CRSs) and user specific reference signals (UE-RS).

FIG. 7 illustrates the structure of an uplink subframe used in LTE(-A).

FIG. 8 illustrates a signal processing procedure for transmitting areference signal (RS) to an uplink.

FIG. 9 illustrates a structure of a demodulation reference signal (DMRS)for a PUSCH.

FIG. 10 illustrates a slot level structure of PUCCH formats 1a and 1b.

FIG. 11 illustrates a carrier aggregation (CA)-based wirelesscommunication system.

FIG. 12 illustrates cross-carrier scheduling.

FIG. 13 illustrates a structure of a self-contained subframe.

FIG. 14 illustrates analog beamforming.

FIG. 15 illustrates signal transmission procedure according to thepresent disclosure.

FIG. 16 illustrates a base station and a user equipment applicable to anembodiment of the present disclosure.

BEST MODE FOR CARRYING OUT THE DISCLOSURE

Embodiments of the present disclosure are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) evolves from 3GPP LTE. While the following description is given,centering on 3GPP LTE/LTE-A for clarity, this is purely exemplary andthus should not be construed as limiting the present disclosure.

In a wireless communication system, a user equipment (UE) receivesinformation through downlink (DL) from a base station (BS) and transmitinformation to the BS through uplink (UL). The information transmittedand received by the BS and the UE includes data and various controlinformation and includes various physical channels according totype/usage of the information transmitted and received by the UE and theBS.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the meantime, the UEmay check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIG. 2 illustrates a radio frame structure. Uplink/downlink data packettransmission is performed on a subframe-by-subframe basis. A subframe isdefined as a predetermined time interval including a plurality ofsymbols. 3GPP LTE supports a type-1 radio frame structure applicable tofrequency division duplex (FDD) and a type-2 radio frame structureapplicable to time division duplex (TDD).

FIG. 2(a) illustrates a type-1 radio frame structure. A downlinksubframe includes 10 subframes each of which includes 2 slots in thetime domain. A time for transmitting a subframe is defined as atransmission time interval (TTI). For example, each subframe has aduration of 1 ms and each slot has a duration of 0.5 ms. A slot includesa plurality of OFDM symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. Since downlink usesOFDM in 3GPP LTE, an OFDM symbol represents a symbol period. The OFDMsymbol may be called an SC-FDMA symbol or symbol period. An RB as aresource allocation unit may include a plurality of consecutivesubcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2(b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 4(5) normalsubframes and 10 special subframes. The normal subframes are used foruplink or downlink according to UL-DL configuration. A subframe iscomposed of 2 slots.

Table 1 shows subframe configurations in a radio frame according toUL-DL configurations.

TABLE 1 Downlink- Uplink- to-Uplink downlink Switch point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U DS U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6  5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is used for initial cell search, synchronization orchannel estimation in a UE and UpPTS is used for channel estimation in aBS and uplink transmission synchronization in a UE. The GP eliminates ULinterference caused by multi-path delay of a DL signal between a UL anda DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3 , a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present disclosure is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 4 illustrates a downlink subframe structure.

Referring to FIG. 4 , a maximum of three (four) OFDM symbols located ina front portion of a first slot within a subframe correspond to acontrol region to which a control channel is allocated. The remainingOFDM symbols correspond to a data region to which a physical downlinkshared chancel (PDSCH) is allocated. A basic resource unit of the dataregion is an RB. Examples of downlink control channels used in LTEinclude a physical control format indicator channel (PCFICH), a physicaldownlink control channel (PDCCH), a physical hybrid ARQ indicatorchannel (PHICH), etc. The PCFICH is transmitted at a first OFDM symbolof a subframe and carries information regarding the number of OFDMsymbols used for transmission of control channels within the subframe.The PHICH is a response of uplink transmission and carries a HARQacknowledgment (ACK)/negative-acknowledgment (NACK) signal. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI includes uplink or downlinkscheduling information or an uplink transmit power control command foran arbitrary UE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. An arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

The PDCCH carries a message known as DCI which includes resourceassignment information and other control information for a UE or UEgroup. In general, a plurality of PDCCHs can be transmitted in asubframe. Each PDCCH is transmitted using one or more CCEs. Each CCEcorresponds to 9 sets of 4 REs. The 4 REs are referred to as an REG. 4QPSK symbols are mapped to one REG. REs allocated to a reference signalare not included in an REG, and thus the total number of REGs in OFDMsymbols depends on presence or absence of a cell-specific referencesignal. The concept of REG (i.e. group based mapping, each groupincluding 4 REs) is used for other downlink control channels (PCFICH andPHICH). That is, REG is used as a basic resource unit of a controlregion. 4 PDCCH formats are supported as shown in Table 2.

TABLE 2 PDCCH Number Number of PDCCH format Number of CCEs (n) of REGsbits 0 1 9 72 1 2 8 144 2 4 36 288 3 5 72 576

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

LTE defines CCE positions in a limited set in which PDCCHs can bepositioned for each UE. CCE positions in a limited set that the UE needsto monitor in order to detect the PDCCH allocated thereto may bereferred to as a search space (SS). In LTE, the SS has a size dependingon PDCCH format. A UE-specific search space (USS) and a common searchspace (CSS) are separately defined. The USS is set per UE and the rangeof the CSS is signaled to all UEs. The USS and the CSS may overlap for agiven UE. In the case of a considerably small SS with respect to aspecific UE, when some CCEs positions are allocated in the SS, remainingCCEs are not present. Accordingly, the BS may not find CCE resources onwhich PDCCHs will be transmitted to available UEs within givensubframes. To minimize the possibility that this blocking continues tothe next subframe, a UE-specific hopping sequence is applied to thestarting point of the USS.

Table 3 shows sizes of the CSS and USS.

TABLE 3 Number of Number of candidates in candidates in PDCCH Number ofcommon dedicated format CCEs (n) search space search space 0 1 — 6 1 2 —6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the USS. Formats 0 and 1Ahave the same size and are discriminated from each other by a flag in amessage. The UE may need to receive an additional format (e.g. format 1,1B or 2 according to PDSCH transmission mode set by a BS). The UEsearches for formats 1A and 1C in the CSS. Furthermore, the UE may beset to search for format 3 or 3A. Formats 3 and 3A have the same size asthat of formats 0 and 1A and may be discriminated from each other byscrambling CRC with different (common) identifiers rather than aUE-specific identifier. PDSCH transmission schemes and informationcontent of DCI formats according to transmission mode (TM) are arrangedbelow.

Transmission Mode (TM)

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO (Multiple Input Multiple        Output)    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (port5) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission mode 9: Transmission through up to 8 layers (ports        7 to 14) or single-antenna port (port 7 or 8) transmission

DCI Format

-   -   Format 0: Resource grants for PUSCH transmission    -   Format 1: Resource assignments for single codeword PDSCH        transmission (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments

FIG. 5 illustrates an EPDCCH. The EPDCCH is a channel additionallyintroduced in LTE-A.

Referring to FIG. 5 , a PDCCH (for convenience, legacy PDCCH or L-PDCCH)according to legacy LTE may be allocated to a control region (see FIG. 4) of a subframe. In the figure, the L-PDCCH region means a region towhich a legacy PDCCH may be allocated. Meanwhile, a PDCCH may be furtherallocated to the data region (e.g., a resource region for a PDSCH). APDCCH allocated to the data region is referred to as an E-PDCCH. Asshown, control channel resources may be further acquired via the E-PDCCHto mitigate a scheduling restriction due to restricted control channelresources of the L-PDCCH region. Similarly to the L-PDCCH, the E-PDCCHcarries DCI. For example, the E-PDCCH may carry downlink schedulinginformation and uplink scheduling information. For example, the UE mayreceive the E-PDCCH and receive data/control information via a PDSCHcorresponding to the E-PDCCH. In addition, the UE may receive theE-PDCCH and transmit data/control information via a PUSCH correspondingto the E-PDCCH. The E-PDCCH/PDSCH may be allocated starting from a firstOFDM symbol of the subframe, according to cell type. In thisspecification, the PDCCH includes both L-PDCCH and EPDCCH unlessotherwise noted.

FIG. 6 illustrates configuration of cell specific reference signals(CRSs) and user specific reference signals (UE-RS). In particular, FIG.6 shows REs occupied by the CRS(s) and UE-RS(s) on an RB pair of asubframe having a normal CP.

In an existing 3GPP system, since CRSs are used for both demodulationand measurement, the CRSs are transmitted in all DL subframes in a cellsupporting PDSCH transmission and are transmitted through all antennaports configured at a BS.

Referring to FIG. 6 , the CRS is transmitted through antenna ports p=0,p=0, 1, p=0, 1, 2, 3 in accordance with the number of antenna ports of atransmission mode. The CRS is fixed to a certain pattern within asubframe regardless of a control region and a data region. The controlchannel is allocated to a resource of the control region, to which theCRS is not allocated, and the data channel is also allocated to aresource of the data region, to which the CRS is not allocated.

A UE may measure CSI using the CRSs and demodulate a signal received ona PDSCH in a subframe including the CRSs. That is, the BS transmits theCRSs at predetermined locations in each RB of all RBs and the UEperforms channel estimation based on the CRSs and detects the PDSCH. Forexample, the UE may measure a signal received on a CRS RE and detect aPDSCH signal from an RE to which the PDSCH is mapped using the measuredsignal and using the ratio of reception energy per CRS RE to receptionenergy per PDSCH mapped RE. However, when the PDSCH is transmitted basedon the CRSs, since the BS should transmit the CRSs in all RBs,unnecessary RS overhead occurs. To solve such a problem, in a 3GPP LTE-Asystem, a UE-specific RS (hereinafter, UE-RS) and a CSI-RS are furtherdefined in addition to a CRS. The UE-RS is used for demodulation and theCSI-RS is used to derive CSI. The UE-RS is one type of DRS. Since theUE-RS and the CRS are used for demodulation, the UE-RS and the CRS maybe regarded as demodulation RSs in terms of usage. Since the CSI-RS andthe CRS are used for channel measurement or channel estimation, theCSI-RS and the CRS may be regarded as measurement RSs.

Referring to FIG. 6 , UE-RSs are transmitted on antenna port(s) p=5,p=7, p=8 or p=7, 8, . . . , ν+6 for PDSCH transmission, where ν is thenumber of layers used for the PDSCH transmission. UE-RSs are present andare a valid reference for PDSCH demodulation only if the PDSCHtransmission is associated with the corresponding antenna port. UE-RSsare transmitted only on RBs to which the corresponding PDSCH is mapped.That is, the UE-RSs are configured to be transmitted only on RB(s) towhich a PDSCH is mapped in a subframe in which the PDSCH is scheduledunlike CRSs configured to be transmitted in every subframe irrespectiveof whether the PDSCH is present.

FIG. 7 illustrates a structure of an uplink subframe used in LTE(-A).

Referring to FIG. 7 , a subframe 500 is composed of two 0.5 ms slots501. Assuming a length of a normal cyclic prefix (CP), each slot iscomposed of 7 symbols 502 and one symbol corresponds to one SC-FDMAsymbol. A resource block (RB) 503 is a resource allocation unitcorresponding to 12 subcarriers in the frequency domain and one slot inthe time domain. The structure of the uplink subframe of LTE(-A) islargely divided into a data region 504 and a control region 505. A dataregion refers to a communication resource used for transmission of datasuch as voice, a packet, etc. transmitted to each UE and includes aphysical uplink shared channel (PUSCH). A control region refers to acommunication resource for transmission of an uplink control signal, forexample, downlink channel quality report from each UE, receptionACK/NACK for a downlink signal, uplink scheduling request, etc. andincludes a physical uplink control channel (PUCCH). A sounding referencesignal (SRS) is transmitted through an SC-FDMA symbol that is lastlypositioned in the time axis in one subframe. SRSs of a plurality of UEs,which are transmitted to the last SC-FDMAs of the same subframe, can bedifferentiated according to frequency positions/sequences. The SRS isused to transmit an uplink channel state to an eNB and is periodicallytransmitted according to a subframe period/offset set by a higher layer(e.g., RRC layer) or aperiodically transmitted at the request of theeNB.

The SRS includes constant amplitude zero auto correlation (CAZAC)sequences. SRSs transmitted from several UEs are CAZAC sequencesr^(SRS)(n)=r_(u,v) ^((α))(n) having different cyclic shift values αaccording to Equation 1.

$\begin{matrix}{{\alpha = {2\pi\;\frac{n_{SRS}^{cs}}{8}}},} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

where n_(SRS) ^(cs) is a value set to each UE by a higher layer and hasan integer value between 0 and 7.

CAZAC sequences generated from one CAZAC sequence through cyclic shifthave zero-correlation values with sequences having different cyclicshift values. Using such property, SRSs of the same frequency domain maybe divided in accordance with CAZAC sequence cyclic shift values. TheSRS of each UE is allocated onto the frequency axis according to aparameter set by the eNB. The UE performs frequency hopping of the SRSso as to transmit the SRS with an overall uplink data transmissionbandwidth.

In order to satisfy a transmission power P_(SRS) of a UE, an SRSsequence r^(SRS)(n) is first multiplied by an amplitude scaling factorβ_(SRS) and then mapped into a resource element (RE) having an index (k,l) from r^(SRS)(0) by the following Equation 2.

$\begin{matrix}{a_{{{2k} + k_{0}},l} = \left\{ {\begin{matrix}{\beta_{SRS}{r^{SRS}(k)}} & {{k = 0},1,\ldots\mspace{14mu},{M_{{sc},b}^{RS} - 1}} \\0 & {otherwise}\end{matrix},} \right.} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

where k₀ denotes a frequency domain start point of the SRS, and M^(RS)_(sc,b) is a length (that is, bandwidth) of a sounding reference signalsequence expressed by a subcarrier unit defined in the followingEquation 3.M _(sc,b) ^(RS) =m _(SRS,b) N _(sc) ^(RB)/2  [Equation 3]

In the Equation 3, m_(SRS,b) denotes an uplink bandwidth N^(UL) _(RB)signaled from the eNB.

FIG. 8 illustrates a signal processing procedure for transmitting areference signal (RS) to an uplink. Data is converted into afrequency-domain signal through a DFT precoder and then transmittedthrough IFFT after frequency mapping. On the other hand, an RS istransmitted without passing through the DFT precoder. Specifically,after an RS sequence is directly generated (S11) in the frequencydomain, the RS is transmitted through sequential processes of localizedmapping (S12), IFFT (S13), and cyclic prefix (CP) attachment (S14).

RS sequence r^((α)) _(u,v)(n) is defined by a cyclic shift a of a basesequence, and may be expressed as the following Equation 4.r _(u,v) ^((α))(n)=e ^(jαn) r _(u,v)(n), 0≤n<M _(sc) ^(RS),  [Equation4]

where M_(sc) ^(RS)=mN_(sc) ^(RB) is a length of the RS sequence, N_(sc)^(RB) is a resource block size expressed in a unit of subcarrier, and mis 1≤m≤N_(RB) ^(max,UL). N_(RB) ^(max,UL) denotes a maximum uplinktransmission band.

Base sequences r _(u,v)(n) are divided into groups. u∈{0, 1, . . . , 29}denotes a group number, and v corresponds to a base sequence numberwithin the corresponding group. Each group includes one base sequence(v=0) of length M_(sc) ^(RS)=mN_(sc) ^(RB) (1≤m≤5) and two basesequences (v=0, 1) of each length M_(sc) ^(RS)=mN_(sc) ^(RB) (6≤m≤N_(RB)^(max,UL)). Each of the sequence group number u and the correspondingnumber v within the corresponding group may vary depending on time. Thedefinition of the base sequence r _(u,v)(0), . . . , r _(u,v)(M_(sc)^(RS)−1) depends on the sequence length M_(sc) ^(RS).

Base sequences of length 3N_(sc) ^(RB) or more may be defined asfollows.

For the base sequence M_(sc) ^(RS)≥3N_(sc) ^(RB), the base sequence r_(u,v)(0), . . . , r _(u,v)(M_(sc) ^(RS)−1) is given by the followingEquation 5.r _(u,v)(n)=x _(q)(n mod N _(ZC) ^(RS)), 0≤n<M _(sc) ^(RS),  [Equation5]

where a qth root Zadoff-Chu sequence may be defined by the followingEquation 6.

$\begin{matrix}{{{x_{q}(m)} = e^{{- j}\;\frac{\pi\;{{qm}{({m + 1})}}}{N_{ZC}^{RS}}}},{0 \leq m \leq {N_{ZC}^{RS} - 1}},} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

where q satisfies the following Equation 7.q=└q+½┘+v·(−1)^(└2q┘)q=N _(ZC) ^(RS)·(u+1)/31,  [Equation 7]

where the length N^(RB) _(ZC) of the Zadoff-Chu sequence is given by thegreatest prime number to satisfy N_(ZC) ^(RS)<M_(sc) ^(RS).

Base sequences of length less than 3N_(sc) ^(RB) may be defined asfollows. First of all, for m_(sc) ^(RS)=N_(sc) ^(RB) and M_(sc)^(RS)=2N_(sc) ^(RB), the base sequences are given by the followingEquation 8.r _(u,v)(n)=e ^(jφ(n)π/4), 0≤n≤M _(sc) ^(RS)−1,  [Equation 8]

where a value of φ(n) for M_(sc) ^(RS)=N_(sc) ^(RB) is given by thefollowing Table 4. A value of φ(n) for M_(sc) ^(RS)=2N_(sc) ^(RB)1 isalso given by a similar Table.

TABLE 4 u φ(0), . . . , φ(11) 0 −1 1 3 −3 3 3 1 1 3 1 −3 3 1 1 1 3 3 3−1 1 −3 −3 1 −3 3 2 1 1 −3 −3 −3 −1 −3 −3 1 −3 1 −1 3 −1 1 1 1 1 −1 −3−3 1 −3 3 −1 4 −1 3 1 −1 1 −1 −3 −1 1 −1 1 3 5 1 −3 3 −1 −1 1 1 −1 −1 3−3 1 6 −1 3 −3 −3 −3 3 1 −1 3 3 −3 1 7 −3 −1 −1 −1 1 −3 3 −1 1 −3 3 1 81 −3 3 1 −1 −1 −1 1 1 3 −1 1 9 1 −3 −1 3 3 −1 −3 1 1 1 1 1 10 −1 3 −1 11 −3 −3 −1 −3 −3 3 −1 11 3 1 −1 −1 3 3 −3 1 3 1 3 3 12 1 −3 1 1 −3 1 1 1−3 −3 −3 1 13 3 3 −3 3 −3 1 1 3 −1 −3 3 3 14 −3 1 −1 −3 −1 3 1 3 3 3 −11 15 3 −1 1 −3 −1 −1 1 1 3 1 −1 −3 16 1 3 1 −1 1 3 3 3 −1 −1 3 −1 17 −31 1 3 −3 3 −3 −3 3 1 3 −1 18 −3 3 1 1 −3 1 −3 −3 −1 −1 1 −3 19 −1 3 1 31 −1 −1 3 −3 −1 −3 −1 20 −1 −3 1 1 1 1 3 1 −1 1 −3 −1 21 −1 3 −1 1 −3 −3−3 −3 −3 1 −1 −3 22 1 1 −3 −3 −3 −3 −1 3 −3 1 −3 3 23 1 1 −1 −3 −1 −3 1−1 1 3 −1 1 24 1 1 3 1 3 3 −1 1 −1 −3 −3 1 25 1 −3 3 3 1 3 3 1 −3 −1 −13 26 1 3 −3 −3 −3 −3 1 −1 −1 3 −1 −3 27 −3 −1 −3 −1 −3 3 1 −1 1 3 −3 −328 −1 3 −3 3 −1 3 3 −3 3 3 −1 −1 29 3 −3 −3 −1 −1 −3 −1 3 −3 3 1 −1

A reference signal for PUSCH is determined as follows.

A reference signal sequence r^(PUSCH)(⋅) for PUSCH is defined byr^(PUSCH)(m·M_(sc) ^(RS)+n)=r_(u,v) ^((α))(n), wherein m and n satisfym=0, 1 and 0, . . . , M_(sc) ^(RS)−1, and M_(sc) ^(RS)=M_(sc) ^(PUSCH).

Cyclic shift in one slot is given by α=2n_(cs)/12 together withn_(cs)=(n_(DMRS) ⁽¹⁾+n_(DMRS) ⁽²⁾+n_(PRS)(n_(s)))mod 12.

n_(DMRS) ⁽¹⁾ is a broadcasted value, n_(DMRS) ⁽²⁾ is given by uplinkscheduling allocation, and n_(PRS)(n_(s)) is a cell-specific cyclicshift value. n_(PRS)(n_(s)) varies depending on a slot number n_(s), andis given by n_(PRS)(n_(s))=Σ_(i=0) ⁷c(8N_(symb) ^(UL)·n_(s)+i)·2^(i).

c(i) is a pseudo-random sequence, and c(i) is a cell-specific value. Apseudo-random sequence generator may be reset to

$c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$at the start of a radio frame.

Table 5 illustrates a cyclic shift field in a Downlink ControlInformation (DCI) format and n_(DMRS) ⁽²⁾.

TABLE 5 Cyclic shift field in DCI format 0 n_(DMRS) ⁽²⁾ 000 0 001 2 0103 011 4 100 6 101 8 110 9 111 10

A physical mapping method for an uplink RS in PUSCH is as follows.

The sequence is multiplied by an amplitude scaling factor β_(PUSCH) andmapped into the same set of physical resource blocks (PRBs) used for acorresponding PUSCH within) a sequence starting with r^(PUSCH)(0). Themapping into resource elements (k,l), with l=3 for normal cyclic prefixand l=2 for extended cyclic prefix, within the subframe is performed insuch a manner that the order of k is increased and then a slot number isincreased.

In summary, if length is 3N_(sc) ^(RB), or more, a ZC sequence is usedwith cyclic extension and, if length is less than 3N_(sc) ^(RB), acomputer generated sequence is used. A cyclic shift is determined inaccordance with a cell-specific cyclic shift, a UE-specific cyclic shiftand a hopping pattern.

FIG. 9 illustrates a structure of a demodulation reference signal (DMRS)for a PUSCH. Referring to FIG. 9 , the DMRS is transmitted throughfourth and eleventh SC-FDMA symbols.

FIG. 10 illustrates PUCCH formats 1a and 1b in case of normal CP. Thesame control information is repeated on a slot basis in a subframe inPUCCH Format 1a and 1b. A UE transmits ACK/NACK signals throughdifferent resources that include different Cyclic Shifts (CSs)(frequency-domain code) of a Computer Generated-Constant Amplitude ZeroAuto Correlation (CG-CAZAC) sequence and an Orthogonal Cover (OC) orOrthogonal Cover Code (OCC) (a time-domain spreading code). The OCincludes, for example, a Walsh/DFT orthogonal code. If the number of CSsis 6 and the number of OCs is 3, a total of 18 UEs may be multiplexed inthe same Physical Resource Block (PRB) based on a single antenna. OCsequences w0, w1, w2 and w3 are applicable to a random time domain(after FFT modulation) or to a random frequency domain (before FFTmodulation). RS signal of each UE is also transmitted through differentresources that include different cyclic shifts of a CG-CAZAC sequenceand orthogonal cover codes w0, w1 and w2.

Length-4 and length-3 OCs for PUCCH Format 1/1a/1b are illustrated inTable 6 and Table 7 below.

TABLE 6 Length-4 orthogonal sequences for PUCCH formats 1/1a/1b Sequenceindex Orthogonal sequences n_(oc)(n_(s)) [w(0) . . . w(N_(SF) ^(PUCCH) −1)] 0 [+1 +1 +1 +1] 1 [+1 −1 +1 −1] 2 [+1 −1 −1 +1]

TABLE 7 Length-3 orthogonal sequences for PUCCH formats 1/1a/1b Sequenceindex Orthogonal sequences n_(oc)(n_(s)) [w(0) . . . w(N_(SF) ^(PUCCH) −1)] 0 [1 1 1] 1 [1 e^(j2π/3) e^(j4π/3)] 2 [1 e^(j4π/3) e^(j2π/3)]

FIG. 11 illustrates carrier aggregation (CA) communication system.

Referring to FIG. 11 , a plurality of UL/DL component carriers (CCs) canbe aggregated to support a wider UL/DL bandwidth. The CCs may becontiguous or non-contiguous in the frequency domain. Bandwidths of theCCs can be independently determined. Asymmetrical CA in which the numberof UL CCs is different from the number of DL CCs can be implemented.Control information may be transmitted/received only through a specificCC. This specific CC may be referred to as a primary CC and other CCsmay be referred to as secondary CCs. For example, when cross-carrierscheduling (or cross-CC scheduling) is applied, a PDCCH for downlinkallocation can be transmitted on DL CC #0 and a PDSCH correspondingthereto can be transmitted on DL CC #2. The term “component carrier” maybe replaced by other equivalent terms (e.g. “carrier”, “cell”, etc.).

For cross-CC scheduling, a carrier indicator field (CIF) is used.Presence or absence of the CIF in a PDCCH can be determined by higherlayer signaling (e.g. RRC signaling) semi-statically and UE-specifically(or UE group-specifically). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: a PDCCH on a DL CC is used to allocate a PDSCH        resource on the same DL CC or a PUSCH resource on a linked UL        CC.    -   No CIF    -   CIF enabled: a PDCCH on a DL CC can be used to allocate a PDSCH        or PUSCH resource on a specific DL/UL CC from among a plurality        of aggregated DL/UL CCs using the CIF.    -   LTE DCI format extended to have CIF    -   CIF corresponds to a fixed x-bit field (e.g. x=3) (when CIF is        set)    -   CIF position is fixed irrespective of DIC format size (when CIF        is set)

When the CIF is present, the BS may allocate a monitoring DL CC (set) toreduce BD complexity of the UE. For PDSCH/PUSCH scheduling, the UE maydetect/decode a PDCCH only on the corresponding DL CCs. The BS maytransmit the PDCCH only through the monitoring DL CC (set). Themonitoring DL CC set may be set UE-specifically, UE-group-specificallyor cell-specifically.

FIG. 12 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH CC. DL CC A˜C may be referred to as a serving CC, servingcarrier, serving cell, etc. When the CIF is disabled, each DL CC cantransmit only a PDCCH that schedules a PDSCH corresponding to the DL CCwithout a CIF according to LTE PDCCH rule (non-cross-CC scheduling).When the CIF is enabled through UE-specific (or UE-group-specific orcell-specific) higher layer signaling, a specific CC (e.g. DL CC A) cantransmit not only the PDCCH that schedules the PDSCH of DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs using the CIF(cross-scheduling). A PDCCH is not transmitted on DL CC B and DL CC C.

In next-generation RAT (Radio Access Technology) a self-containedsubframe is considered in order to minimize data transmission latency.FIG. 13 illustrates a self-contained subframe structure. In FIG. 13 , ahatched region represents a DL control region and a black regionrepresents a UL control region. A blank region may be used for DL datatransmission or UL data transmission. DL transmission and ULtransmission are sequentially performed in a single subframe, and thusDL data can be transmitted and UL ACK/NACK can also be received in asubframe. Consequently, a time taken until data retransmission isperformed when a data transmission error is generated is reduced andthus final data delivery latency can be minimized.

As examples of self-contained subframe types which can beconfigured/set, the following four subframe types can be considered.Respective periods are arranged in a time sequence.

-   -   DL control period+DL data period+GP (Guard Period)+UL control        period    -   DL control period+DL data period    -   DL control period+GP+UL data period+UL control period    -   DL control period+GP+UL data period

A PDFICH, a PHICH and a PDCCH can be transmitted in the data controlperiod and a PDSCH can be transmitted in the DL data period. A PUCCH canbe transmitted in the UL control period and a PUSCH can be transmittedin the UL data period. The GP provides a time gap in a process in whicha BS and a UE switch from a transmission mode to a reception mode or ina process in which the BS and the UE switch from the reception mode tothe transmission mode. Some OFDM symbols in a subframe at a time when DLswitches to UL may be set to the GP.

Furthermore, in a millimeter wave (mmW) system, a wavelength of a signalis short, so that a multitude of antennas can be installed in the samearea. For example, since the wavelength is 1 cm in a 30 GHz band, atotal of 100 antenna elements can be installed in a 5-by-5 cm2 panel ina form of a two-dimensional array with a 0.5λ (wavelength) spacing.Therefore, in the mmW system, a plurality of antenna elements are usedto increase a beamforming (BF) gain to increase a coverage or increase athroughput.

In this connection, when each antenna element has a TXRU (transceiverunit) so that transmission power and phase can be adjusted for eachantenna element, independent beamforming may be realized for eachfrequency resource. However, installing each TXRU in each of all 100antenna elements is ineffective in terms of cost. Therefore, a scheme ofmapping a plurality of antenna elements to one TXRU and adjusting adirection of the beam with an analog phase shifter is considered. Thisanalog beamforming scheme may form only one beam direction in a fullband, and has a disadvantage that a frequency selective beam cannot beachieved. Thus, as an intermediate form between digital BF and analogBF, a hybrid BF in which B TXRUs map to Q antenna elements (B<Q) may beconsidered. In this case, a number of directions of a beam in which thebeam is simultaneously transmitted is limited to a number smaller thanor equal to B, though it varies depending on a connection scheme betweenthe B TXRUs and Q antenna elements.

FIG. 14 illustrates analog beamforming. Referring to FIG. 14 , atransmitter may transmit a signal while changing a direction of the beamover time (transmit beamforming). A receiver may also receive a signalwhile changing a direction of the beam over time (receive beamforming).Within a certain time interval, (i) directions of the transmit andreceive beams may change simultaneously over time, (ii) a direction ofthe transmit beam may be fixed over time, while only a direction of thereceive beam may change over time, or (iii) a direction of the receivebeam may be fixed over time, while only a direction of the transmit beammay change over time.

EMBODIMENT

As described before, the new RAT system is highly likely to beimplemented in such a manner that an eNB and a UE performtransmission/reception (Tx/Rx) (analog or hybrid) beamforming based onmmW properties. A plurality of beam directions (e.g., represented bybeam IDs/indexes or port IDs/indexes) may be available to the eNB andthe UE, and the best Tx/Rx beam (hereinafter, referred to as a servingbeam) among beams may be changed over time due to a radio channelenvironment and the mobility of the UE. Accordingly, a Tx/Rx beamalignment procedure for updating a serving beam may be performedaccording to a specific period or upon occurrence of an event (e.g.,when reception performance is decreased to or below a predeterminedlevel) in a multi-beam operation situation. For the convenience, an RSused for beam alignment is referred to as a beam refinement RS (BRRS).

The present disclosure proposes a data scheduling method and a signalprocessing/handling method in a Tx/Rx beam alignment situation. For theconvenience, a time unit for data scheduling is defined as a slot. Theterm slot may be replaced with transmission time interval (TTI),subframe, and so on. To help the understanding of the presentdisclosure, it is assumed that an SRS is used as a BRRS (referred to asa UL BRRS) in a UL Tx/Rx beam alignment procedure, whereas a CSI-RS isused as a BRRS (referred to as a DL BRRS) in a DL Tx/Rx beam alignmentprocedure. Accordingly, a transmission end and a reception end for theUL BRRS may be described as a UE Tx beam and an eNB Rx beam,respectively. Likewise, a transmission end and a reception end for theDL BRRS may be described as an eNB Tx beam and a UE eNB Rx beam,respectively. Further, the term Tx/Rx beam (direction) may be usedinterchangeably with its equivalent terms Tx/Rx beam ID (or index) orTx/Rx port ID (or index). In the following description, puncturing mayinclude rate-matching. The puncturing includes, but not limited to,generating modulation symbols according to the amount of allocated Txresources (e.g., RBs or Res) and dropping some data symbol(s) accordingto the amount of actual available Tx resources. The rate-matchingincludes generating data modulation symbols according to the amount ofactual available Tx resources.

UL Beam Alignment and UL Data Scheduling

The following may be considered as SRS (i.e., UL BRRS)transmission-based UL Tx/Rx beam alignment procedures. In each option, aUL data scheduling method and a UE operation method are proposed. Thepresent disclosure is based on the assumption that a time unit for ULdata scheduling is a slot and thus a UE Tx beam (direction) and an eNBRx beam (direction) for UL data are allocated/configured on a slot basis(that is, the same allocation/configuration is applied throughout aslot).

(1) Option 1

A. Tx/Rx beam alignment method

i. An SRS is transmitted in a plurality of symbols (all symbols or theremaining symbols except for a specific small number of symbols) in aslot. A symbol includes an OFDM(A) symbol or SC-FDM(A) symbol.

ii. A UE Tx beam (direction) is changed one or more times in a slot orchanged in each symbol (group) (in the slot). A symbol group includesone or more consecutive symbols.

iii. An eNB Rx beam (direction) is changed on a slot basis (fixed withina slot).

iv. An SRS transmitted in the above manner is referred to as a“beam-sweep SRS”.

B. UL Data Scheduling and UE Operation

i. Alt 1: Case in which simultaneous transmission of a beam-sweep SRSand UL data (e.g., a PUSCH) (multiplexed with the SRS in FDM) in thesame slot is not allowed/supported for a UE.

1. If a beam-sweep SRS and UL data are simultaneouslyscheduled/indicated (for transmission in the same slot), the UE maytransmit only the beam-sweep SRS, while dropping the UL datatransmission). Herein, it does not matter whether resources (e.g., REs)allocated to the beam-sweep SRS and the UL data overlap with each other.If the beam-sweep SRS is transmitted only during a partial period in theslot, the UE may transmit the UL data during a time period without thebeam-sweep SRS (through puncturing/rate matching). Since HARQ is appliedto the UL data, transmission of UL data may be favorable even though itis partial. A UE Tx beam (direction) configured for UL data transmissionmay be applied to the UL data. However, if the length (e.g., in symbols)of a time period during which the UL data is transmittable is equal toor less than a specific value (e.g., 3 symbols) or a DMRS is notincluded in the time period during which the UL data is transmittable,the whole UL data transmission may be dropped.

2. The same operation principle may be applied to beam-sweep SRStransmission and UL control transmission (e.g., a PUCCH) (transmitted inFDM with a corresponding SRS). In this case, since the PUCCH has ahigher protection priority than the SRS, only the PUCCH may betransmitted, while the SRS is dropped, or one of the two may be dropped,with the other transmitted according to the type of UCI delivered on thePUCCH. For example, if the UCI type is HARQ-ACK or SR, only the PUCCH istransmitted while the SRS is dropped. On the other hand, if the UCI typeis CSI, only the SRS is transmitted while the PUCCH is dropped.

In regard to beam-sweep SRS transmission and UL data (e.g., PUSCH)transmission (in FDM with a corresponding SRS), one of the two may bedropped with the other transmitted according to whether UL data and UCIare multiplexed in the PUSCH. For example, if there is no UCImultiplexed with UL data in the PUSCH, only the SRS may be transmittedwhile the PUSCH may be dropped. On the other hand, if UL data ismultiplexed with UCI in the PUSCH, only the PUSCH may be transmittedwhile the SRS may be dropped. Or one of the two may be dropped with theother transmitted according to the type of the UCI multiplexed with theUL data. For example, if the UCI type is HARQ-ACK, only the PUSCH may betransmitted while the SRS may be dropped. On the other hand, if the UCItype is CSI, only the SRS may be transmitted while the PUSCH may bedropped.

ii. Alt 2: Case in which simultaneous transmission of a beam-sweep SRSand UL data (e.g., a PUSCH) (multiplexed with the SRS in FDM) in thesame slot is allowed/supported for a UE.

1. Since a UE Tx beam (direction) for beam-sweep SRS transmission ischanged on a symbol (symbol group) basis, the UE may map/transmit a DMRSto/in each of the symbols (symbol groups) of a UL data channel.

2. A beam-sweep SRS and a UL data signal which are mapped to the samesymbol (symbol group) may be transmitted based on the same UE Tx beam(direction) (e.g., configured for transmission of the SRS). That is, theUL data may be transmitted by applying the same UE. Tx beam (direction)as configured for the SRS transmission to the UL data transmission, anda DMRS for the UL data may be transmitted additionally each time the UETx beam (direction) configured for the SRS transmission is changed. Itdoes not matter whether resources (e.g., REs) allocated to thebeam-sweep SRS and the UL data overlap with each other. When thebeam-sweep SRS is transmitted only during a partial period in a slot,the UE may transmit the UL data during a time period without thebeam-sweep SRS in the slot according to an original configuration (e.g.,a Tx beam (direction) configured for the UL data, DMRS mapping, and soon).

iii. For beam alignment across a plurality of slots, a plurality ofslots allocated as beam-sweep SRS transmission resources may beconfigured non-contiguously (with a specific period).

(2) Option 2

A. Tx/Rx Beam Alignment Method

i. An SRS is transmitted in a plurality of symbols (all symbols or theremaining symbols except for a specific small number of symbols) in aslot. A symbol includes an OFDM(A) symbol or SC-FDM(A) symbol.

ii. A UE Tx beam (direction) is changed on a slot basis (fixed within aslot).

iii. An eNB Rx beam (direction) is changed one or more times within aslot or changed on a symbol (symbol group) basis (within the slot). Asymbol group includes one or more consecutive symbols.

iv. An SRS transmitted in the above manner is referred to as a“beam-repeat SRS”.

B. UL Data Scheduling and UE Operation

i. Since UE Tx beams (directions) of both of a beam-repeat SRS and ULdata are changed on a slot basis, simultaneous transmission of thebeam-repeat SRS and the UL data (e.g., a PUSCH) (multiplexed with theSRS in FDM) may be allowed/supported for a UE.

1. The above operation may be limited to a case in which the same UE Txbeam (direction) is indicated for the beam-repeat SRS transmission andthe UL data transmission. If resources (e.g., REs) allocated to the twoUL signals overlap with each other, the UE may perform the SRStransmission, while for the UL data, the UE may a) map/transmit nosignal to/in the overlapped resources (by puncturing) or b) drop thewhole UL data transmission.

2. If different UE Tx beams (beam directions) are indicated fortransmission of a beam-repeat SRS and transmission of UL data, the UEmay transmit only the SRS, while dropping the UL data transmission.

3. If different Tx beams (beam directions) are indicated fortransmission of a beam-repeat SRS and transmission of UL data, the UEmay transmit both of the beam-repeat SRS and the UL data (e.g., PUSCH)(multiplexed with the SRS in FDM) in the same slot by applying the samesingle Tx beam (direction) as configured for the SRS transmission to theUL data transmission. When the beam-repeat SRS is transmitted onlyduring a partial time period in a slot, the UE may apply an original UETx beam (direction) indicated for the UL data during a time periodwithout the beam-repeated SRS in the slot, and a UE Tx beam (direction)configured for the SRS transmission during a time period with thebeam-repeated SRS. However, if there is a time period with a DMRS in thetime period to which the original HE Tx beam (direction) indicated forthe UL data is applied and the time period to which the UE Tx beam(direction) configured for the SRS transmission is applied, the UE maya) map/transmit no signal (by puncturing) or b) additionallymap/transmit a DMRS, for the UL data in the time period.

ii. For beam alignment across a plurality of slots, a plurality of slotsallocated as beam-repeat SRS transmission resources may be configurednon-contiguously (with a specific period).

(3) Option 3

A. Tx/Rx Beam Alignment Method

i. An SRS is transmitted in a plurality of symbols (all symbols or theremaining symbols except for a specific small number of symbols) in aslot. A symbol includes an OFDM(A) symbol or SC-FDM(A) symbol, and asymbol group includes one or more consecutive symbols.

ii. Case in which the number of SRS transmission symbols (symbol groups)in a single slot is 1 or larger.

1. Case 1: A UE Tx beam (direction) is changed one or more times withina slot or changed on a symbol (symbol group) basis (in the slot), and aneNB Rx beam (direction) is changed on a slot basis (fixed within aslot).

2. Case 2: A UE Tx beam (direction) is changed on a slot basis (fixedwithin a slot), and an eNB Rx beam (direction) is changed one or moretimes within a slot or changed on a symbol (symbol group) basis (in aslot).

iii. An SRS transmitted in the above manner is referred to as a“single-beam SRS”.

B. UL Data Scheduling and UE Operation

i. Simultaneous transmission of a single-beam SRS and UL data (e.g., aPUSCH) within the same slot may be allowed/supported for one UE.

1. Case 1: If the same Tx beam (direction) is indicated for transmissionof a single-beam SRS and transmission of UL data, without overlapbetween resources (REs) of the two UL signals, the UE may transmit thetwo UL signals (simultaneously). If the resources (REs) of the two ULsignals overlap with each other, the UE may a) map/transmit no signalonly in the overlapped resources (or only in SRS transmission symbols)(by puncturing), for the UL data, while transmitting the SRS, or b)transmit the UL data, while dropping the SRS transmission.

2. Case 2: If different UE Tx beams (beam directions) are indicated fortransmission of a single-beam SRS and transmission of UL data, the UEmay a) map/transmit no signal only in SRS transmission symbols (bypuncturing), for the UL data, while transmitting the SRS, or b) transmitthe UL data, while dropping the SRS transmission. Further, c) the UE maytransmit both of the single-beam SRS and the UL data (e.g., a PUSCH)(multiplexed with the SRS in FDM) in the same slot by applying the sameUE Tx beam as configured for the SRS transmission to the transmission ofthe UL data only in the SRS transmission symbols. In the case of c), anoriginal UE Tx beam (direction) indicated for the UL data may be appliedto the transmission of the UL data in symbols carrying no SRS.

3. Case 3: If the number of SRS transmission symbols (symbol groups) is1 or larger in a single slot, the UE may apply the operation describedin Case 1/2 a) on an SRS symbol (group) basis or b) commonly to all SRSsymbols (symbol groups).

ii. For beam alignment across a plurality of slots, a plurality of slotsallocated as single-beam SRS transmission resources may be configuredcontiguously, or non-contiguously (with a specific period). A timeinterval between adjacent allocated slots (i.e., an allocation slotperiod) may be set to be smaller in Option 3 than in Option 1/2.

(4) Related Issues

A. In the beam alignment procedures (particularly, in Option 1/2),whether simultaneous transmission of a UL BRRS (e.g., beam-sweep SRS orbeam-repeat SRS) and UL data in the same slot is allowed/supported for aUE may be configured/signaled to the UE (by the eNB).

i. For example, whether simultaneous transmission of a beam-sweep orbeam-repeat SRS and UL data in the same slot is available or UL datatransmission is unavailable in a slot configured with transmission of abeam-sweep or beam-repeat SRS may be configured/signaled.

B. UE Tx beams (beam directions) may be determined as follows forapplication to transmission of UL data and transmission of a UL BRRS(e.g., beam-sweep SRS, beam-repeat SRS, or single-beam SRS). Thefollowing methods may be used in combination under circumstances.

i. Alt 1: A UE Tx beam (direction) may be indicated individually foreach of UL data and an SRS. For example, the UE Tx beam (direction) ofthe UL data may be indicated by Layer 1 (L1) signaling (e.g., a PDCCH).Further, the UE Tx beam (direction) of the SRS may be predefinedaccording to a symbol (group)/slot index or signaled by higher-layersignaling (e.g., RRC signaling).

ii. Alt 2: The same UE Tx beam (direction) as indicated for UL datatransmission may be applied to transmission of an SRS.

iii. Alt 3: It may be assumed that the same UE Tx beam (direction) isapplied to transmission of two UL signals (particularly, in Option 2/3).For example, the same UE Tx beam (direction) as configured for SRStransmission may be applied to UL data transmission.

FIG. 15 illustrates an exemplary signal transmission procedure accordingto the present disclosure. The above methods may be used in combinationfor signal transmission of a UE.

Referring to FIG. 15 , after receiving scheduling information for ULdata (S1502), a UE may transmit the UL data in a time slot including aplurality of symbols, using the scheduling information (S1504). If an RSfor beam alignment is not transmitted in the time slot, a Tx beamdirection for the UL data may be maintained the same throughout the timeslot. On the contrary, if the RS for beam alignment is transmitted inthe time slot, the Tx beam direction of the UL data may be changed tomatch a Tx beam direction of the RS for beam alignment in a symbolcarrying the RS for beam alignment. An original Tx beam directionconfigured for the UL data may be different from the Tx beam directionof the RS for beam alignment. If the Tx beam direction of the UL data ischanged to match the Tx beam direction of the RS for beam alignment, anRS for demodulation of the UL data may be transmitted additionally inone or more symbols carrying the RS for beam alignment. Further, in thetime slot, the Tx beam direction of the RS for beam alignment may bechanged on a symbol group basis, and the Tx beam direction of the ULdata may also be changed on a symbol group basis to match the Tx beamdirection of the RS for beam alignment. Further, the wirelesscommunication system may include a 3^(rd) generation partnership project(3GPP)-based wireless communication system.

DL Beam Alignment and DL Data Scheduling

The following may be considered aa CSI-RS (i.e., DL BRRS)transmission-based DL Tx/Rx beam alignment procedures. In each option, aDL data scheduling method and a UE operation method are proposed. Thepresent disclosure is based on the assumption that a time unit for DLdata scheduling is a slot and thus an eNB Tx beam (direction) and a UERx beam (direction) for DL data are allocated/configured on a slot basis(that is, the same allocation/configuration is applied throughout aslot).

(1) Option 1

A. A Tx/Rx Beam Alignment Method

i. A CSI-RS is transmitted in a plurality of symbols (all symbols or theremaining symbols except for a specific small number of symbols) in aslot. A symbol includes an OFDM(A) symbol.

ii. A UE Rx beam (direction) is changed one or more times in a slot orchanged on a symbol (symbol group) basis (in the slot). A symbol groupincludes one or more consecutive symbols.

iii. An eNB Tx beam (direction) is changed on a slot basis (fixed withina slot).

iv. A CSI-RS transmitted in the above manner is referred to as a“beam-sweep CSI-RS”.

B. DL Data Scheduling and UE Operation

i. Alt 1: Case in which simultaneous transmission of a beam-sweep CSI-RSand DL data (e.g., a PDSCH) (multiplexed with the CSI-RS in FDM) in thesame slot is not allowed/supported for a UE.

1. A beam-sweep CSI-RS and DL data (multiplexed with the CSI-RS in FDM)are simultaneously scheduled/indicated (for transmission in the sameslot), the UE may receive only the beam-sweep CSI-RS, while dropping theDL data reception. Herein, it does not matter whether resources (e.g.,REs) allocated to the beam-sweep CSI-RS and the DL data overlap witheach other. If the beam-sweep CSI-RS is transmitted only during apartial time period in a slot, the UE may receive the DL data during atime period without the beam-sweep CSI-RS (through puncturing/ratematching) in the slot. Since HARQ is applied to the DL data, receptionof DL data may be favorable even though it is partial. A UE Rx beam(direction) configured for DL data transmission may be applied to the DLdata. However, if the length (e.g., in symbols) of a time period duringwhich the DL data is transmittable is equal to or less than a specificvalue (e.g., 3 symbols) or a DMRS is not included in the time periodduring which the DL data is transmittable, the whole DL data receptionmay be dropped.

2. For the above-described (and later-described) dropped DL data, the UEmay a) map and transmit an HARQ-ACK feedback as NACK or b) drop theHARQ-ACK transmission.

ii. Alt 2: Case in which simultaneous transmission of a beam-sweepCSI-RS and DL data (multiplexed with the CSI-RS in FDM) in the same slotis allowed/supported for a UE.

1. Since a UE Rx beam (direction) for beam-sweep CSI-RS reception ischanged on a symbol (symbol group) basis, a DMRS may be mapped to andtransmitted in each of the symbols (symbol groups) of a DL data channel.

2. A beam-sweep CSI-RS and a DL data signal which are mapped to the samesymbol (symbol group) may be transmitted based on the same UE Rx beam(direction) (e.g., configured for transmission of the CSI-RS). That is,the DL data may be transmitted by applying the same UE Rx beam(direction) as configured for the CSI-RS transmission to the DL datatransmission, and a DMRS for the DL data may be transmitted additionallyeach time the UE Rx beam (direction) configured for the CSI-RStransmission is changed. It does not matter whether resources (e.g.,REs) allocated to the beam-sweep CSI-RS and the DL data overlap witheach other. When the beam-sweep CSI-RS is received only during a partialtime period in a slot, the UE may receive the DL data according to anoriginal configuration (e.g., an Rx beam (direction) configured for theDL data, DMRS mapping, and so on) during a time period without thebeam-sweep CSI-RS in the slot.

iii. For beam alignment across a plurality of slots, a plurality ofslots allocated as beam-sweep CSI-RS transmission resources may beconfigured non-contiguously with a specific period).

(2) Option 2

A. Tx/Rx Beam Alignment Method

i. A CSI-RS is transmitted in a plurality of symbols (all symbols or theremaining symbols except for a specific small number of symbols) in aslot. A symbol includes an OFDM(A) symbol.

ii. A UE Rx beam (direction) is changed on a slot basis (fixed within aslot).

iii. An eNB Tx beam (direction) is changed one or more times in a slotor changed on a symbol (group) basis (in the slot). A symbol groupincludes one or more consecutive symbols.

iv. A CSI-RS transmitted in the above manner is referred to as a“beam-repeat CSI-RS”.

B. DL Data Scheduling and UE Operation

i. Since UE Rx beams (beam directions) of both a beam-repeat CSI-RS andDL data are changed on a slot basis, simultaneous transmission of thebeam-repeat CSI-RS and the DL data (e.g., a PDSCH) (multiplexed with theCSI-RS in FDM) may be allowed/supported for a UE.

1. The above operation may be limited to a case in which the same Rxbeam (direction) is indicated for the beam-repeat CSI-RS transmissionand the DL data transmission. If resources (e.g., REs) allocated to thetwo DL signals overlap with each other, the UE may perform the CSI-RSreception, while for the DL data, the UE may a) map/receive no signalonly to/in the overlapped resources (by puncturing) or b) drop the wholeDL data reception.

2. If different UE Rx beams (beam directions) are indicated fortransmission of a beam-repeat CSI-RS and transmission of DL data, the UEmay receive only the CSI-RS, while dropping the DL data reception.

3. If different UE Rx beams (beam directions) are indicated forreception of a beam-repeat CSI-RS and transmission of DL data, the UEmay receive both of the beam-repeat CSI-RS and the DL data (e.g., aPDSCH) (transmitted with the CSI-RS in FDM) in the same slot by applyingthe same UE Rx beam (direction) as configured for the CSI-RS receptionto the DL data reception. When the beam-repeat CSI-RS is received onlyduring a partial time period in a slot, the UE may apply an original UERx beam (direction) indicated for the DL data during a time periodwithout the beam-repeated CSI-RS in the slot, and a UE Rx beam(direction) configured for the CSI-RS transmission during a time periodwith the beam-repeated CSI-RS. However, if there is a time period with aDMRS in the time period to which the original UE Tx beam (direction)indicated for the UL data is applied and the time period to which the UETx beam (direction) configured for the CSI-RS transmission is applied,the eNB may a) map/transmit no signal (by puncturing) or b) additionallymap/transmit a DMRS, for the DL data in the time period.

ii. For beam alignment across a plurality of slots, a plurality of slotsallocated as beam-repeat CSI-RS transmission resources may be configurednon-contiguously (with a specific period).

(3) Option 3

A. Tx/Rx Beam Alignment Method

i. A CSI-RS is transmitted in a plurality of symbols (all symbols or theremaining symbols except for a specific small number of symbols) in aslot. A symbol includes an OFDM(A) symbol, and a symbol group includesone or more consecutive symbols.

ii. Case in which the number of CSI-RS transmission symbols (symbolgroups) in a single slot is 1 or larger.

1. Case 1: A UE Rx beam (direction) is changed one or more times in aslot or changed on a symbol (symbol group) basis (in the slot), and aneNB Tx beam (direction) is changed on a slot basis (fixed within aslot).

2. Case 2: A UE Rx beam (direction) is changed on a slot basis (fixedwithin a slot), and an eNB Tx beam (direction) is changed one or moretimes in a slot or on a symbol (symbol group) basis (in the slot).

iii. A CSI-RS transmitted in the above manner is referred to as a“single-beam CSI-RS”.

B. DL Data Scheduling and UE Operation

i. Simultaneous transmission of a single-beam CSI-RS and DL data (e.g.,a PDSCH) in the same slot may be allowed/supported for one UE.

1. Case 1: If the same UE Rx beam (direction) is indicated fortransmission of a single-beam CSI-RS and transmission of DL data,without overlap between resources (REs) of the two DL signals, the UEmay receive the two DL signals (simultaneously). If the resources (REs)of the two DL signals overlap with each other, the UE may a)map/transmit no signal only in the overlapped resources (or only inCSI-RS transmission symbols) (by puncturing), for the DL data, whilereceiving the CSI-RS, or b) receive the DL data, while dropping theCSI-RS reception.

2. Case 2: If different UE Rx beams (beam directions) are indicated fortransmission of a single-beam CSI-RS and transmission of DL data, the UEmay a) map/receive no signal only in CSI-RS transmission symbols (bypuncturing), for the DL data, while receiving the CSI-RS, or b) receivethe DL data, while dropping the CSI-RS reception. Further, c) the UE mayreceive both of the single-beam CSI-RS and the DL data (e.g., PDSCH)(transmitted with the CSI-RS in FDM) in the same slot by applying thesame UE Rx beam as configured for the CSI-RS transmission to thereception of the DL data only in the CSI-RS transmission symbols. In thecase of c), an original UE Rx beam (direction) indicated for the DL datamay be applied to the reception of the DL data in symbols carrying noCSI-RS.

3. Case 3: If the number of CSI-RS transmission symbols (symbol groups)in a single slot is 1 or larger, the UE may apply the operationdescribed in Case 1/2 a) on a CSI-RS symbol (group) basis or b) commonlyto all CSI-RS symbols (symbol groups).

ii. For beam alignment across a plurality of slots, a plurality of slotsallocated as single-beam CSI-RS transmission resources may be configuredcontiguously, or non-contiguously (with a specific period). A timeinterval between adjacent allocated slots (i.e., an allocation slotperiod) may be set to be smaller in Option 3 than in Option 1/2.

(4) Related Issues

A. In the beam alignment procedures (particularly, in Option 1/2),whether simultaneous reception of a DL BRRS (e.g., beam-sweep CSI-RS orbeam-repeat CSI-RS) and DL data in the same slot is allowed/supportedfor a UE may be configured/signaled to the UE (by the eNB).

i. For example, whether simultaneous reception of a beam-sweep or abeam-repeat CSI-RS and DL data in the same slot is available or DL datareception is unavailable in a slot configured with transmission of abeam-sweep or beam-repeat CSI-RS may be configured/signaled.

B. A UE Rx beam (direction) (and/or an eNB Tx beam (direction)) may bedetermined as follows for application to transmission of DL data andtransmission of a DL BRRS (e.g., beam-sweep CSI-RS, beam-repeat CSI-RS,or single-beam CSI-RS). The following methods may be used in combinationunder circumstances.

i. Alt 1: A UE Rx beam (direction) (and/or an eNB Tx beam (direction))may be indicated individually for each of DL data and a CSI-RS. Forexample, a UE Rx beam (direction) for DL data may be indicated by Layer1 (L1) signaling (e.g., a PDCCH). Further, a UE Rx beam (direction)(and/or an eNB Tx beam (direction)) for a CSI-RS may be predefinedaccording to a symbol (group)/slot index or signaled by higher-layersignaling (e.g., RRC signaling).

ii. Alt 2: The same UE Rx beam (direction) (and/or an eNB Tx beam(direction)) as indicated for DL data transmission may be applied totransmission of a CSI-RS.

iii. Alt 3: It may be assumed that the same UE Rx beam (direction)(and/or the same eNB Tx beam (direction)) is applied to transmission oftwo DL signals (particularly, in Option 2/3). For example, the same UERx beam (direction) (and/or the same eNB Tx beam (direction)) configuredfor CSI-RS transmission may be applied to DL data reception.

The UE operation methods (signal processing and handling methods)proposed in the present disclosure are not limited to a UL/DL BRRStransmission situation configured for the purpose of UL/DL beamalignment. The same operation principle of the proposed methods may alsobe applied to transmission of a UL SRS and a DL CSI-RS which areconfigured in a normal situation (e.g., similarly to Option 2/3).

FIG. 16 illustrates a BS and a UE of a wireless communication system,which are applicable to embodiments of the present disclosure.

Referring to FIG. 16 , the wireless communication system includes a BS110 and a UE 120. When the wireless communication system includes arelay, the BS or UE may be replaced by the relay.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present disclosure. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present disclosure. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal.

The embodiments of the present disclosure described hereinbelow arecombinations of elements and features of the present disclosure. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent disclosure may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent disclosure may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present disclosure or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present disclosure, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present disclosure may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentdisclosure may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to UEs, eNBs or other apparatusesof a wireless mobile communication system.

What is claimed is:
 1. A method of controlling a downlink signal by auser equipment (UE) in a wireless communication system, the methodcomprising: receiving downlink scheduling information, wherein thedownlink scheduling information includes scheduling information fordownlink data in a first slot; and receiving CSI-RS(Channel StateInformation Reference Signal) for performing beam alignment detection onplural symbols in the first slot, wherein based on a downlinktransmission beam direction of the CSI-RS being same on the pluralsymbols, the downlink data is not received on the plural symbols.
 2. Themethod according to claim 1, wherein a downlink reception beam directionis changed on the plural symbols.
 3. The method according to claim 1,wherein a downlink transmission beam direction of the CSI-RS is changedon a slot basis, the downlink reception beam direction is changed on asymbol basis.
 4. The method according to claim 1, wherein based on thedownlink reception beam direction that is set same on the plural symbolsin the first slot, transmitting NACK (Negative Acknowledgement) inresponse to the downlink data.
 5. The method according to claim 1,wherein frequency resources assigned to the CSI-RS and the downlink dataare different.
 6. A user equipment (UE) used in a wireless communicationsystem, comprising: a radio frequency (RF) module; and a processor,wherein: the processor is configured to receive scheduling information,the downlink scheduling information includes scheduling information fordownlink data in a first slot, the processor is configured to receiveCSI-RS (Channel State Information Reference Signal) for performing beamalignment detection on plural symbols in the first slot, wherein basedon a downlink transmission beam direction of the CSI-RS being same onthe plural symbols, the downlink data is not received on the pluralsymbols.
 7. The UE according to claim 6, wherein a downlink receptionbeam direction is changed on the plural symbols.
 8. The UE according toclaim 6, wherein a downlink transmission beam direction of the CSI-RS ischanged on a slot basis, the downlink reception beam direction ischanged on a symbol basis.
 9. The UE according to claim 6, wherein basedon the downlink reception beam direction that is set same on the pluralsymbols in the first slot, transmitting NACK (Negative Acknowledgement)in response to the downlink data.
 10. The UE according to claim 6,wherein frequency resources assigned to the CSI-RS and the downlink dataare different.